The present invention relates to a semiconductor device and a manufacturing method thereof, and can be suitably used in a semiconductor device including, for example, a titanium film as a barrier metal film and a tungsten film as a material of a wiring layer and the like.
A multi-layer wiring structure is generally applied as a wiring structure of a semiconductor device. In the semiconductor device, an interlayer insulating film is formed to cover a semiconductor substrate over which a semiconductor element is formed, and the multi-layer wiring structure is formed over the interlayer insulating film. A damascene process is used as one process of forming the wiring.
In the damascene process, wiring trenches, corresponding to the pattern of the wiring layer, are formed in the insulating film. Next, a predetermined conductive film is formed to cover the insulating film with a barrier metal film interposed in the wiring trench. Next, a polishing process is performed to remove a portion of the conductive film located over the upper surface of the insulating film, so that the wiring layer is formed in the wiring trench.
In some semiconductor devices, a tungsten film is applied as a conductive film, and a laminated film of a titanium film (lower layer) and a titanium nitride film (upper layer) is applied as a barrier metal film. In order to form the tungsten film so as to fill a wiring trench, the tungsten film is formed by a CVD (Chemical Vapor Deposition) process. When the tungsten film is formed by a CVD process, tungsten hexafluoride (WF6) is used as a material gas.
When the tungsten film is formed by tungsten hexafluoride, the tungsten hexafluoride may react with the titanium film of the underlying barrier metal film, thereby causing adhesiveness to decrease. This phenomenon becomes remarkable particularly in the outer peripheral portion of the semiconductor substrate where the thickness of the titanium nitride film covering the titanium film is small. Therefore, the problem that the tungsten film is peeled off due to the physical load applied during the polishing process of the tungsten film occurs remarkably in the outer peripheral portion of the semiconductor substrate (wafer).
In order to solve this problem, for example, Japanese Unexamined Patent Application Publication No. Hei 10(1998)-107032 proposes a technique of suppressing peeling of the tungsten film, in which the tungsten film is not formed in the outer peripheral portion of the semiconductor substrate by clamping the outer peripheral portion thereof with a clamp ring.
Further, Japanese Unexamined Patent Application Publication No. Hei 7(1995)-273045 proposes a technique of using two types of clamps when the tungsten film is formed. The proposed technique is as follows: in the stage of growing the nucleus of tungsten, a contact-type clamp, closely adhered to the outer peripheral portion of the semiconductor substrate, is used to prevent tungsten hexafluoride from wrapping around the outer peripheral portion thereof; and in the stage of forming a tungsten film as a bulk, the tungsten film is formed in the outer peripheral portion thereof by using a spaced clamp, spaced apart from the outer peripheral portion thereof.
Furthermore, Japanese Unexamined Patent Application Publication No. Hei 11(1999)-145085 proposes a technique of suppressing peeling of the tungsten film by nitriding the titanium film exposed in the outer peripheral portion of the semiconductor substrate to form a titanium nitride film.